ram12345,
I'm not 100% certain that I understand what you're trying to accomplish but you will likely want to change the query type to show totals (on the design tab). Then change the total value from 'Group By' to 'Sum' for both columns.
If you want to perform division on this value in the query, I believe you'll have to create a second query as I don't think you can perform a calculation directly on an aggregated value in the same query.
The second query would pull the values in from the first query and the divide them there.
If you don't need the query, you can probably skip the second query and just get both values using 2 separate dlookups. (or dsums to skip the totals function).
dim dblValue1 as double
dim dblValue2 as double
dim dblNewValue as double
dblValue1 = dlookup("[sumofValueA]","qryMyQuery")
dblValue2 = dlookup("[sumofValueB]","qryMyQuery")
dblNewValue = dblValue1 / dblValue2
Gunner